Importance of Formic Acid in Various Ethological States of Oecophylla smaragdina (Fabricius)

Abstract

In polymorphic colony of Oecophylla smaragdina Fabricus, the content of formic acid (FA) in major workers was 9.7 ± 0.7 mg/gm tissue which was one forth of the content of minor workers, one third of the content of intermediate workers and 10 times higher than non-biting reproductive forms. Larvae and pupae had no traces of FA in their body. During the 24 h cycle, the major workers showed a chemical rhythm in content of FA with a peak at noon and low amounts in morning, evening and night. The workers aggressively defend enemies by painful bite with sharp mandibles and simultaneous spray of FA and some of them continued biting until they died, at which time the FA content decreased to non-detectable amounts and the body weight was reduced to 60 % of the original weight. Continuous disturbance caused an increase in the content of FA in workers. Continuous bite for 30 min resulted in a significant increase in the content of protein together with a decrease in the content of free amino acids (FAA) and complete stoppage of activity of transaminase enzymes together with a sharp decline in uric acid and urea in both head and thorax. Slight but significant decrease in glucose together with no significant change in the contents of glycogen and lactic acid after 30 min of biting highlights the efficiency of insect tracheal system in supplying O₂. A sharp increase in acetylcholine (Ach) in head and thorax may be the reason for the observed immobility or lack of coordination in movements in ants after biting. The observed hyper-proteinemia in ants within 30 min was evidenced by additional bands in electrophorogram.